Pattern forming material and pattern forming method

ABSTRACT

A pattern forming material includes a binary copolymer represented by the following general formula or a ternary or higher copolymer obtained by further polymerizing the binary copolymer with another group:                    
     wherein R 1  indicates a hydrogen atom or an alkyl group; R 2  and R 3  independently indicate a hydrogen atom, an alkyl group, a phenyl group or an alkenyl group or together indicate a cyclic alkyl group, a cyclic alkenyl group, a cyclic alkyl group having a phenyl group or a cyclic alkenyl group having a phenyl group; R 4  indicates a hydrogen atom or an alkyl group; x satisfies a relationship of 0&lt;x&lt;1; and y satisfies a relationship of 0&lt;y&lt;1.

This application is a Divisional of application Ser. No. 09/551,656filed Apr. 18, 2000, now U.S. Pat. No. 6,306,556B1 which is a Divisionalof application Ser. No. 09/326,541 filed Jun. 7, 1999 and now U.S. Pat.No. 6,120,974, which is a Divisional of application Ser. No. 08/805,702filed Feb. 25, 1997 and now U.S. Pat. No. 5,965,325.

BACKGROUND OF THE INVENTION

The present invention relates to a fine-line pattern forming method foruse in a manufacturing process for a semiconductor IC device and thelike, and a material for forming a pattern used in the pattern formingmethod.

In the manufacture of ICs, LSIs and the like, a pattern isconventionally formed through photolithography using UV, in which alight source with a shorter wavelength has become mainly used inaccordance with refinement of a semiconductor device. Recently, asurface imaging process using dry development has been developed inorder to increase the depth of focus and improve practical resolution inusing a light source with a shorter wavelength.

As an example of the surface imaging process, U.S. Pat. No. 5,278,029discloses a method in which, after selectively forming a polysiloxanefilm on the surface of a resist film of a resist material which cangenerate an acid through exposure, the resist film is dry etched byusing the polysiloxane film as a mask, so as to form a resist pattern.

Now, this conventional method of forming the resist pattern will bedescribed with reference to FIGS. 5(a) through 5(d).

In this method, a copolymer of1,2,3,4-tetrahydronaphthyridinenimino-p-styrene sulfonate (NISS) andmethyl methacrylate (MMA) is used as the resist material for generatingan acid through exposure.

First, as is shown in FIG. 5(a), a resist film 401, which generates anacid through exposure, coated on a semiconductor substrate 400 isirradiated with a KrF excimer laser 404 by using a mask 403, and thus,the acid is generated in an exposed area 401 a of the resist film 401.Owing to this acid, the exposed area 401 a is changed to be hydrophilic,so that water in air can be easily adsorbed by the exposed area 401 a.As a result, a thin water absorbing layer 405 is formed in the vicinityof the surface of the exposed area 401 a as is shown in FIG. 5(b).

Next, when an alkoxysilane gas 406 is introduced onto the surface of theresist film 401, the acid generated on the surface of the exposed area401 a works as a catalyst, so that alkoxysilane is hydrolyzed anddehydrated. As a result, an oxide film 407 is formed on the surface ofthe exposed area 401 a as is shown in FIG. 5(c). Subsequently, when theresist film 401 is dry etched by RIE using O₂ plasma 408 by using theoxide film 407 as a mask, a fine-line resist pattern 409 is formed as isshown in FIG. 5(d).

This pattern forming method thus adopts a negative type lithographyprocess for forming a resist pattern in an exposed area, in which theacid generated in the exposed area of the resist film is used as thecatalyst for selectively forming the oxide film in the exposed area andthe oxide film is used as a mask in the dry etching for forming theresist pattern.

The negative type lithography process has the following problems in, forexample, forming a contact hole for connecting multilayeredinterconnections of an IC:

First, usage of a mask generally adopted in pattern exposure can causethe following problem: In the lithography for forming a contact hole,the aperture ratio of the mask is very high when the negativelithography process is used. Specifically, while a light shielding filmagainst exposing light is formed merely in a portion corresponding tothe contact hole on the mask, the light shielding film is removed andquartz of the mask substrate is bare in the other portion excluding thecontact hole in order to transmit the exposing light. Since the areaoccupied by all the contact holes in the entire area of a semiconductorchip is generally very small, the proportion of the area occupied by thebare quartz to the area of the light shielding film on the mask becomeshigh, namely, the aperture ratio of the mask becomes high.

When the aperture ratio of the mask is high, the effect of ambient dustsis increased. Specifically, dusts adhered to the light shielding film onthe mask scarcely affect the process, but those adhered to thetransparent portion of the mask change this portion into a lightshielding portion. When the exposure is effected by using the mask towhich dusts are thus adhered, a pattern defect is caused in the portionto which the dusts are adhered. In this manner, since the aperture ratioof the mask is high in the negative type lithography process, theprocess can be easily affected by dusts, resulting in easily decreasingthe yield.

Secondly, in the lithography process for forming a contact hole, ahalf-tone type mask can be used for the purpose of increasing the depthof focus. However, the effect of increasing the depth of focus can beattained merely in a positive type lithography but cannot be attained inthe negative type lithography. Accordingly, in the formation of acontact hole, the depth of focus is smaller in the negative type processthan in the positive type process.

The occurrence of these first and second problems are not limited to theformation of a contact hole, but can be caused in the cases where a maskhaving a larger area of the transparent portion is used and where thedepth of focus is desired to be increased.

SUMMARY OF THE INVENTION

In view of the aforementioned conventional problems, the object of theinvention is realizing a positive type surface imaging processreplaceable with the negative type surface imaging process.

In order to achieve this object, a resist film including an acidic or abasic group is selectively irradiated with an energy beam in thisinvention, so that a basic or an acidic group having the reverseproperty to that of the group included in the resist film can begenerated in an exposed area. Alternatively, after generating an acidicor a basic group in an exposed area by selectively irradiating a resistfilm with an energy beam, the entire surface of the resist film isirradiated with another energy beam, so that a basic or an acidic grouphaving the reverse property to that of the group generated in theexposed area can be generated on the entire surface of the resist film.Thus, neutralization is effected in the exposed area of the resist film,and in an unexposed area of the resist film, the acidic or the basicgroup works as a catalyst for forming an oxide film. In this manner, apositive type surface imaging process, which cannot be attained by theconventional method, can be realized by this invention.

The first pattern forming material of this invention comprises acopolymer including a first group for generating a base throughirradiation with an energy beam and a second group having an acidicproperty.

When the resist film formed out of the first pattern forming material isselectively irradiated with the energy beam, the first group isdissolved into the base in the exposed area on the resist film, so thatthe generated base is neutralized with the second group having theacidic property, while the unexposed area on the resist film remains tobe acidic. Accordingly, since merely the unexposed area on the resistfilm can selectively retain its acidic property, the positive typesurface imaging process can be realized.

The second group in the first pattern forming material is preferably agroup including a sulfonic acid group. In this case, owing to the strongacidic property of sulfonic acid, sulfonic acid can exhibit its strongcatalytic function in the formation of the metal oxide film in theunexposed area on the resist film. Therefore, the strong acidic propertycan be selectively retained merely in the unexposed area on the resistfilm.

The copolymer in the first pattern forming material is preferably abinary copolymer represented by the following general formula or aternary or higher copolymer obtained by further polymerizing the binarycopolymer with another group:

Chemical Formula 1:

wherein R₁ indicates a hydrogen atom or an alkyl group; R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a is phenyl group; R₄ indicates a hydrogen atom oran alkyl group; x satisfies a relationship of 0<x<1; and y satisfies arelationship of 0<y<1.

In this case, since sulfonic acid can exhibit its strong catalyticfunction in the formation of the metal oxide film in the unexposed areaon the resist film, the strong acidic property can be selectivelyretained in the unexposed area on the resist film. On the other hand, inthe exposed area on the resist film, since amine having a strong basicproperty is generated, sulfonic acid having a strong acidic property canbe completely neutralized. Accordingly, the strong acidic property canbe selectively retained merely in the unexposed area on the resist film.

The second pattern forming material of this invention comprises acopolymer including a first group for generating an acid throughirradiation with an energy beam and a second group having a basicproperty.

When the resist film formed out of the second pattern forming materialis selectively irradiated with the energy beam, the first group isdissolved into the acid in the exposed area on the resist film, so thatthe generated acid can be neutralized with the second group having thebasic property, while the unexposed area on the resist film remains tobe basic. Accordingly, merely the unexposed area on the resist film canselectively retain the basic property, resulting in realizing thepositive type surface imaging process.

The first group in the second pattern forming material is preferably agroup for generating sulfonic acid. In this case, owing to the strongacidic property of sulfonic acid, the exposed area on the resist filmcan be completely neutralized, while the unexposed area on the resistfilm remains to be basic. Accordingly, the unexposed area of the resistfilm can selectively retain the basic property.

The copolymer in the second pattern forming material is preferably abinary copolymer represented by the following general formula or aternary or higher copolymer obtained by further polymerizing the binarycopolymer with another group:

Chemical Formula 2:

wherein R₅ indicates a hydrogen atom or an alkyl group; R₆ and R₇independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group; R₈ indicates a hydrogen atom or analkyl group; x satisfies a relationship of 0<x<1; and y satisfies arelationship of 0<y<1.

In this case, amine can exhibit its strong catalytic function in theformation of the metal oxide film in the unexposed area on the resistfilm, so that the unexposed area on the resist film can selectivelyretain the strong basic property. On the other hand, in the exposed areaof the resist film, since sulfonic acid having a strong acidic propertyis generated, amine having a strong basic property can be completelyneutralized. Accordingly, merely the unexposed area on the resist filmcan selectively retain the strong basic property.

The third pattern forming material of this invention comprises acopolymer including a first group for generating an acid throughirradiation with a first energy beam having a first energy band; and asecond group for generating a base through irradiation with a secondenergy beam having a second energy band different from the first energyband.

In the resist film formed out of the third pattern forming material, theacid is generated through the irradiation with the first energy beam,and the base is generated through the irradiation with the second energybeam. Accordingly, when the pattern exposure of the resist film usingthe first energy beam is effected and then the entire surface exposureusing the second energy beam is effected, in the exposed area of thefirst energy beam on the resist film, the acid generated through thepattern exposure using the first energy beam is neutralized with thebase generated through the entire surface exposure using the secondenergy beam. On the other hand, the unexposed area of the first energybeam on the resist film attains a basic property through the entiresurface exposure using the second energy beam. Contrarily, when thepattern exposure of the resist film using the second energy beam iseffected and then the entire surface exposure using the first energybeam is effected, in the exposed area of the second energy beam on theresist film, the base generated through the pattern exposure using thesecond energy beam is neutralized with the acid generated through theentire surface exposure using the first energy beam. On the other hand,the unexposed area of the second energy beam on the resist film attainsan acidic property through the entire surface exposure using the firstenergy beam. Accordingly, the positive type surface imaging process canbe realized.

Furthermore, since the third pattern forming material comprises thecopolymer including the first group for generating the acid through theirradiation with the first energy beam and the second group forgenerating the base through the irradiation with the second energy beam,the acid or the base cannot be generated until the irradiation with theenergy beam, namely, the resist film remains to be neutral until theirradiation with the energy beam. Accordingly, the pattern formingmaterial can be prevented from being changed in its property by an acidor a base during pre-baking, resulting in forming a stable resist film.

The first group in the third pattern forming material is preferably agroup for generating sulfonic acid. Ih this case, when the patternexposure is effected by using the first energy beam, owing to the strongacidic property of sulfonic acid, the exposed area of the first energybeam on the resist film can be completely neutralized, while theunexposed area of the first energy beam on the resist film retains thebasic property. Accordingly, merely the unexposed area of the firstenergy beam on the resist film can selectively retain the basicproperty. Contrarily, when the pattern exposure is effected by using thesecond energy beam, the unexposed area of the second energy beam on theresist film can exhibit a strong catalytic function in the formation ofthe oxide film. Accordingly, merely the unexposed area of the secondenergy beam on the resist film can selectively retain the strong acidicproperty.

The copolymer in the third pattern forming material is preferably abinary copolymer represented by the following general formula or aternary or higher copolymer obtained by further polymerizing the binarycopolymer with another group:

Chemical Formula 3:

wherein R₉ indicates a hydrogen atom or an alkyl group; R₁₀ and R₁₁independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group; R₁₂ indicates a hydrogen atom or analkyl group; R₁₃ and R₁₄ independently indicate a hydrogen atom, analkyl group, a phenyl group or an alkenyl group, or together indicate acyclic alkyl group, a cyclic alkenyl group, a cyclic alkyl group havinga phenyl group or a cyclic alkenyl group having a phenyl group; xsatisfies a relationship of 0<x<1; and y satisfies a relationship of0<y<1.

In this case, sulfonic acid having a strong acidic property is generatedthrough the irradiation of the resist film with the first energy beam,and amine having a strong basic property is generated through theirradiation with the second energy beam. Therefore, when the patternexposure is effected by using the first energy beam, the unexposed areaof the first energy beam on the resist film retains the strong basicproperty, while the exposed area of the first energy beam on the resistfilm can be completely neutralized. Contrarily, when the patternexposure is effected by using the second energy beam, the unexposed areaof the second energy beam on the resist film retains the strong acidicproperty, while the exposed area of the second energy beam on the resistfilm can be completely neutralized.

The first pattern forming method of this invention comprises a firststep of forming a resist film by coating a semiconductor substrate witha pattern forming material including a copolymer having a first groupfor generating a base through irradiation with an energy beam and asecond group having an acidic property; a second step of selectivelyirradiating the resist film with the energy beam by using a mask havinga desired pattern, generating the base in an exposed area on the resistfilm and neutralizing the generated base with the second group; a thirdstep of supplying metal alkoxide onto the resist film and forming ametal oxide film on a surface of an unexposed area on the resist film;and a fourth step of forming a resist pattern by dry-etching the resistfilm by using the metal oxide film as a mask.

According to the first pattern forming method, through the irradiationof the resist film with the energy beam, the generated base isneutralized with the second group having the acidic property in theexposed area on the resist film, while the unexposed area on the resistfilm remains to be acidic. When the metal alkoxide is supplied to theresist film, the metal oxide film cannot be formed in the exposed areabecause the exposed area on the resist film has been neutralized, butthe metal oxide film is selectively formed in the unexposed area on theresist film. Accordingly, through the dry etching of the resist filmusing the metal oxide film as a mask, it is possible to form a fine-linepositive type resist pattern having a satisfactory shape.

Furthermore, according to the first pattern forming method, the acidworks as the catalyst in the formation of the metal oxide film in theunexposed area on the resist film, and hence, the resultant metal oxidefilm can attain a high density and sufficient strength.

In the first pattern forming method, the third step preferably includesa step of allowing the unexposed area on the resist film to adsorbwater. In this case, since water can be diffused into a deep portionfrom the surface of the unexposed area on the resist film, the metaloxide film formed on the surface of the unexposed area on the resistfilm can attain a large thickness.

In the first pattern forming method, the second group is preferably agroup including a sulfonic acid group. In this case, owing to the strongacidic property of sulfonic acid, it is possible to form the metal oxidefilm having a sufficient density in the unexposed area on the resistfilm by using the strong catalytic function of sulfonic acid. As aresult, the selectivity in the dry etching can be improved. Thus, it ispossible to form a more fine-line positive type resist pattern having asatisfactory shape.

The copolymer used in the first pattern forming method is preferably abinary copolymer represented by the following general formula or aternary or higher copolymer obtained by further polymerizing the binarycopolymer with another group:

Chemical Formula 4:

wherein R₁ indicates a hydrogen atom or an alkyl group; R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group; R₄ indicates a hydrogen atom or analkyl group; x satisfies a relationship of 0<x<1; and y satisfies arelationship of 0<y<1.

In this case, since sulfonic acid can exhibit its strong catalyticfunction in the formation of the metal oxide film in the unexposed areaon the resist film, the unexposed area on the resist film canselectively retain the strong acidic property. Therefore, the metaloxide film having a sufficient density can be formed by supplying themetal alkoxide. Furthermore, in the exposed area on the resist film,since amine having a strong basic property is generated, sulfonic acidhaving a strong acidic property can be completely neutralized.Therefore, the metal oxide film cannot be formed in the exposed area. Inthis manner, the selectivity in the dry etching is high, and hence, itis possible to form a more fine-line positive type resist pattern havinga satisfactory shape.

The second pattern forming method of this invention comprises a firststep of forming a resist film by coating a semiconductor substrate witha pattern forming material including a copolymer having a first groupfor generating an acid through irradiation with an energy beam and asecond group having a basic property; a second step of selectivelyirradiating the resist film with the energy beam by using a mask havinga desired pattern, generating the acid in an exposed area on the resistfilm and neutralizing the generated acid with the second group; a thirdstep of supplying metal alkoxide onto the resist film and forming ametal oxide film on a surface of an unexposed area on the resist film;and a fourth step of forming a resist pattern by dry-etching the resistfilm by using the metal oxide film as a mask.

According to the second pattern forming method, through the irradiationof the resist film with the energy beam, the generated acid isneutralized with the second group having the basic property in theexposed area on the resist film, while the unexposed area on the resistfilm remains to be basic. When the metal alkoxide is supplied to theresist film, the metal oxide film cannot be formed in the exposed areabecause the exposed area on the resist film has been neutralized, butthe metal oxide film is selectively formed in the unexposed area on theresist film. Accordingly, through the dry etching of the resist filmusing the metal oxide film as a mask, it is possible to form a fine-linepositive type resist pattern having a satisfactory shape.

Furthermore, according to the second pattern forming method, the baseworks as a catalyst in the formation of the metal oxide film in theunexposed area on the resist film. Therefore, the speed for forming themetal oxide film can be improved, resulting in improving throughput.

In the second pattern forming method, the third step preferably includesa step of allowing the unexposed area on the resist film to adsorbwater. In this case, since water is diffused into a deep portion fromthe surface of the unexposed area on the resist film, the metal oxidefilm formed in the unexposed area on the resist film can attain a largethickness.

In the second pattern forming method, the first group is preferably agroup for generating sulfonic acid. In this case, owing to the strongacidic property of sulfonic acid, the exposed area on the resist filmcan be completely neutralized, while the unexposed area on the resistfilm retains the basic property. Therefore, the metal oxide film can beformed merely in the unexposed area on the resist film with highselectivity. Accordingly, it is possible to form a more fine-linepositive resist pattern having a satisfactory shape.

The copolymer used in the second pattern forming method is preferably abinary copolymer represented by the following general formula or aternary or higher copolymer obtained by further polymerizing the binarycopolymer with another group:

Chemical Formula 5:

wherein R₅ indicates a hydrogen atom or an alkyl group; R₆ and R₇independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group; R₈ indicates a hydrogen atom or analkyl group; x satisfies a relationship of 0<x<1; and y satisfies arelationship of 0<y<1.

In this case, in the unexposed area on the resist film, amine exhibitsits strong catalytic function, and hence, the metal oxide film with asufficient density can be formed. On the other hand, in the exposed areaon the resist film, since sulfonic acid having a strong acidic propertyis generated, amine having a strong basic property can be completelyneutralized. As a result, the selectivity in the dry etching is veryhigh, and it is possible to form a more fine-line positive resistpattern having a satisfactory shape.

The third pattern forming method of this invention comprises a firststep of forming a resist film by coating a semiconductor substrate witha pattern forming material including a copolymer having a first groupfor generating an acid through irradiation with a first energy beamhaving a first energy band and a second group for generating a basethrough irradiation with a second energy beam having a second energyband different from the first energy band; a second step of selectivelyirradiating the resist film with the first energy beam by using a maskhaving a desired pattern, and generating the acid in an exposed area ofthe first energy beam on the resist film; a third step of irradiating anentire surface of the resist film with the second energy beam,generating the base on the entire surface of the resist film, andneutralizing the generated base with the acid generated in the exposedarea of the first energy beam on the resist film; a fourth step ofsupplying metal alkoxide onto the resist film and forming a metal oxidefilm on a surface of an unexposed area of the first energy beam on theresist film; and a fifth step of forming a resist pattern by dry-etchingthe resist film by using the metal oxide film as a mask.

According to the third pattern forming method, in the exposed area ofthe first energy beam on the resist film, since the acid generatedthrough the pattern exposure using the first energy beam is neutralizedwith the base generated through the entire surface exposure using thesecond energy beam, the metal oxide film cannot be formed in the exposedarea. On the other hand, in the unexposed area of the first energy beamon the resist film, since the base is generated through the entiresurface exposure using the second energy beam, the metal oxide film canbe formed owing to the catalytic function of the base by supplying themetal alkoxide to the resist film. Accordingly, through the dry etchingof the resist film using the metal oxide film as a mask, a positive typeresist pattern can be formed.

Furthermore, according to the third pattern forming method, since thebase works as the catalyst in the formation of the metal oxide film inthe unexposed area of the first energy beam on the resist film, thespeed for forming the metal oxide film can be improved, resulting inimproving the throughput.

In the third pattern forming method, the first group is preferably agroup for generating sulfonic acid. In this case, owing to the strongacidic property of sulfonic acid, the exposed area of the first energybeam on the resist film can be completely neutralized, while theunexposed area of the first energy beam on the resist film retains thebasic property. Accordingly, the metal oxide film can be formed merelyin the unexposed area of the first energy beam on the resist film withvery high selectivity. As a result, it is possible to form a morefine-line positive type resist pattern having a satisfactory shape.

The fourth pattern forming method of this invention comprises a firststep of forming a resist film by coating a semiconductor substrate witha pattern forming material including a copolymer having a first groupfor generating a base through irradiation with a first energy beamhaving a first energy band and a second group for generating an acidthrough irradiation with a second energy beam having a second energyband different from the first energy band; a second step of selectivelyirradiating the resist film with the first energy beam by using a maskhaving a desired pattern, and generating the base in an exposed area ofthe first energy beam on the resist film; a third step of irradiating anentire surface of the resist film with the second energy beam,generating the acid on the entire surface of the resist film, andneutralizing the generated acid with the base generated in the exposedarea of the first energy beam on the resist film; a fourth step ofsupplying metal alkoxide onto the resist film and forming a metal oxidefilm on a surface of an unexposed area of the first energy beam on theresist film; and a fifth step of forming a resist pattern by dry-etchingthe resist film by using the metal oxide film as a mask.

According to the fourth pattern forming method, in the exposed area ofthe first energy beam on the resist film, since the base generatedthrough the pattern exposure using the first energy beam is neutralizedwith the acid generated through the entire surface exposure using thesecond energy beam, the metal oxide film cannot be formed in the exposedarea. On the other hand, in the unexposed area of the first energy beamon the resist film, since the acid is generated through the entiresurface exposure using the second energy beam, the metal oxide film canbe formed owing to the catalytic function of the acid by supplying themetal alkoxide. Accordingly, through the dry etching of the resist filmusing the metal oxide film as a mask, a positive type resist pattern canbe formed.

Furthermore, according to the fourth pattern forming method, since themetal oxide film can be formed owing to the catalytic function of theacid in the unexposed area of the first energy beam on the resist film,the resultant metal oxide film can attain a high density and sufficientstrength.

In the fourth pattern forming method, the second group is preferably agroup for generating sulfonic acid In this case, since sulfonic acid isa strong acid, it is possible to form a metal oxide film having asufficient density in the unexposed area of the first energy beam on theresist film owing to the strong catalytic function of sulfonic acid. Asa result, the selectivity in the dry etching is high, and it is possibleto form a more fine-line positive type resist pattern having asatisfactory shape.

In the third or fourth pattern forming method, the fourth steppreferably includes a step of allowing the unexposed area on the resistfilm to adsorb water. In this case, since water is diffused into a deepportion from the surface of the unexposed area of the first energy beamon the resist film, the metal oxide film formed in the unexposed areacan attain a large thickness.

The copolymer used in the third or fourth pattern forming method ispreferably a binary copolymer represented by the following generalformula or a ternary or higher copolymer obtained by furtherpolymerizing the binary copolymer with another group:

Chemical Formula 6:

wherein R₉ indicates a hydrogen atom or an alkyl group; R₁₀ and R₁₁independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group; R₁₂ indicates a hydrogen atom or analkyl group; R₁₃ and R₁₄ independently indicate a hydrogen atom, analkyl group, a phenyl group or an alkenyl group, or together indicate acyclic alkyl group, a cyclic alkenyl group, a cyclic alkyl group havinga phenyl group or a cyclic alkenyl group having a phenyl group; xsatisfies a relationship of 0<x<1; and y satisfies a relationship of0<y<1.

When the copolymer represented by Chemical Formula 6 is used in thethird pattern forming method, since sulfonic acid generated through thepattern exposure using the first energy beam is neutralized with aminegenerated through the entire surface exposure using the second energybeam, the metal oxide film cannot be formed in the exposed area of thefirst energy beam on the resist film. On the other hand, in theunexposed area of the first energy beam on the resist film, since aminehaving a strong basic property is generated through the entire surfaceexposure using the second energy beam, the metal oxide film with asufficient density can be formed by supplying the metal alkoxide to theresist film. Accordingly, the selectivity in the dry etching is veryhigh, and it is possible to form a more fine-line positive resistpattern having a satisfactory shape.

When the copolymer represented by Chemical Formula 6 is used in thefourth pattern forming method, since amine generated through the patternexposure using the first energy beam is neutralized with sulfonic acidgenerated through the entire surface exposure using the second energybeam, the metal oxide film cannot be formed in the exposed area of thefirst energy beam on the resist film. On the other hand, in theunexposed area of the first energy beam on the resist film, sincesulfonic acid having a strong acidic property is generated through theentire surface exposure using the second energy beam, the metal oxidefilm with a sufficient density can be formed by supplying the metalalkoxide. Accordingly, the selectivity in the dry etching is very high,and it is possible to form a more fine-line positive type resist patternhaving a satisfactory shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) through 1(d) are sectional views for showing procedures of apattern forming method according to a first embodiment of the invention;

FIGS. 2(a) through 2(d) are sectional views for showing procedures of apattern forming method according to a second embodiment of theinvention;

FIGS. 3(a) through 3(c) are sectional views for showing procedures of apattern forming method according to a third embodiment of the invention;

FIGS. 4(a) and 4(b) are sectional views for showing other procedures ofthe pattern forming method of the third embodiment; and

FIGS. 5(a) through 5(d) are sectional views for showing procedures of aconventional pattern forming method.

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1)

FIGS. 1(a) through 1(d) are sectional views for showing procedures of apattern forming method of a first embodiment.

As a resist material, a copolymer represented by Chemical Formula 7dissolved in diglyme is used.

Chemical Formula 7:

First, as is shown in FIG. 1(a), the resist material is spin-coated on asemiconductor substrate 100 of silicon, and the resultant semiconductorsubstrate is annealed at a temperature of 90° C. for 90 seconds, therebyforming a resist film 101 with a thickness of 1 μm. At this point, nopeeling is observed, and the resist film 101 has satisfactory adhesion.Then, by using a mask 103, the substrate is irradiated with a KrFexcimer laser 104, i.e., an energy beam, thereby transferring a patternof the mask 103 onto the resist film 101. In this manner,O-acryloyl-acetophenone-oxime (AAPO) is dissolved to generate amine onthe surface of an exposed area 101 a of the resist film 101. A reactioncaused through the exposure of the resist material is shown as ChemicalFormula 8.

Chemical Formula 8:

An unexposed area 101 b of the resist film 101 has a strong acidicproperty owing to the function of a sulfonic acid group in ChemicalFormula 7. On the other hand, in the exposed area 101 a of the resistfilm 101, AAPO in Chemical Formula 7 is dissolved into amine having abasic property, and the amine neutralizes the acidic property resultingfrom the function of the sulfonic acid group. At this point, since theunexposed area 101 b has the strong acidic property, water is moreeasily adsorbed in the unexposed area 101 b than in the exposed area 101a which has been neutralized. In other words, since the unexposed area101 b includes the group having the strong acidic property, a hydrogenbond with water is strengthened in the unexposed area 101 b, and hencewater can be easily adsorbed. In contrast, in the exposed area 101 a, ahydrogen bond with water is weakened by the neutralization, and watercannot be easily adsorbed.

Next, as is shown in FIG. 1(b), the semiconductor substrate 100 isallowed to stand in air with a relative humidity of 95% at a temperatureof 30° C. for 30 minutes, thereby supplying water vapor 105 onto thesurface of the resist film 101. In this manner, the water vapor 105 isadsorbed by the surface of the unexposed area 101 b, which can easilyadsorb water, and the adsorbed water is diffused into a deep portion,for example, at a depth of 100 nm from the surface of the unexposed area101 b. Since the exposed area 101 a has been neutralized, water isdifficult to be adsorbed. Thus, a water adsorbing layer 106 isselectively formed in the unexposed area 101 b.

Then, as is shown in FIG. 1(c), while retaining the semiconductorsubstrate 100 in the air with the relative humidity of 95% at atemperature of 30° C., vapor 107 of methyltriethoxysilane (MTEOS), i.e.,metal alkoxide, is sprayed onto the surface of the resist film 101 for 3minutes, thereby selectively forming an oxide film 108 on the surface ofthe unexposed area 101 b of the resist film 101. In this case, an acid(H⁺) derived from sulfonic acid works as a catalyst in hydrolysis anddehydration of MTEOS, so that the oxide film 108 can be formed.Therefore, the oxide film 108 is formed merely a portion where both H⁺serving as the catalyst and water are present.

According to the first embodiment, the oxide film is not formed in theexposed area 101 a of the resist film 101 because sulfonic acid isneutralized by the generated amine and loses its function as thecatalyst and water cannot be easily adsorbed in the exposed area 101 a.On the other hand, the oxide film 108 is formed in the unexposed area101 b of the resist film 101 because H⁺ serving as the catalyst ispresent and a sufficient amount of water has been adsorbed in theunexposed area 101 b.

Next, as is shown in FIG. 1(d), by using the oxide film 108 as a mask,the semiconductor substrate 100 is subjected to RIE (reactive ionetching) using O₂ plasma 109, thereby forming a resist pattern 110. Inthis case, the RIE using O₂ plasma is effected by using a parallel platereactive ion etching system under conditions of a power of 900 W, apressure of 0.7 Pa and a flow rate of 40 SCCM.

In this embodiment, since the oxide film 108 is selectively formed inthe unexposed area 101 b alone and the etching is effected by using theoxide film 108, the positive type resist pattern 110 having a verticalsection can be formed in the unexposed area 101 b.

“Furthermore, since the water vapor 105 is supplied to the resist film101 in the procedure shown in FIG. 1(b), water is diffused into the deepportion from the surface of the unexposed area 101 b of the resist film101, so that the oxide film 108 can be grown toward the inside of theresist film 101. As a result, the oxide film 108 can attain a largethickness.

In addition, since MTEOS is supplied to the resist film 101 in the airwith the relative humidity of 95% in the procedure shown in FIG. 1(c),equilibrium of water can be retained so that the water having beenadsorbed by the resist film 101 can be prevented from evaporating andthat water can be supplied in a sufficient amount for the formation ofthe oxide film 108. As a result, the resultant oxide film 108 can attaina thickness sufficiently large for withstanding the RIE using O₂ plasma.”

After the supply of MTEOS, the resist film 101 can be allowed to standin vacuum so as to evaporate alcohol included in the oxide film 108.Thus, the flow of the oxide film 108 can be avoided.

In this manner, the resist film 101 of the resist material including anacidic group is subjected to the pattern exposure in this embodiment. Inthe exposed area 101 a, a base is generated to neutralize the acidicproperty of the exposed area 101 a, and the oxide film 108 isselectively formed in the unexposed area 101 b alone, so as to be usedin etching the resist film 101. Accordingly, it is possible to form thepositive type fine-line resist pattern 110 having a satisfactory shape.

Also, since water is forcedly adsorbed in the unexposed area 101 bbefore forming the oxide film 108, the resultant oxide film 108 canattain a large thickness required for the dry development by the RIEusing O₂ plasma.

In the resist material used in the first embodiment, the copolymerrepresented by Chemical Formula 7 includes styrene sulfonic acid as theacidic group. However, the acidic group is not limited to styrenesulfonic acid but can be any group having a strong acidic property andincluding a group represented by Chemical Formula 9.

Chemical Formula 9:

Furthermore, MTEOS is used as the metal alkoxide in this embodiment, butMTEOS can be replaced with any other metal alkoxide in a gas or liquidphase such as Si(OCH₃)₄(tetramethoxysilane),Si(OC₂H₅)₄(tetraethoxysilane), Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃, andZr(OC₂H₅)₃.

Also, the dry development is effected by the RIE using O₂ plasma in thisembodiment, but ECR (electron cyclotron resonance etching) using O₂plasma is adoptable instead.

Moreover, a light source for the exposure is the KrF excimer laser inthis embodiment, but an i-line, an ArF excimer laser, EB, X-rays or thelike can be used.

Furthermore, in the procedure for diffusing water in the surface of theunexposed area 101 b of the resist film 101 in this embodiment, thesemiconductor substrate 100 is allowed to stand in the water vapor, butwater in a liquid phase can be supplied to the resist film 101 on thesemiconductor substrate 100 instead. However, water can be more rapidlydiffused and the thickness of the oxide film 108 can be more increasedwhen the water is supplied in a gas phase than in a liquid phase, andhence, water is preferably supplied in a gas phase.

(Embodiment 2)

FIGS. 2(a) through 2(d) are sectional views for showing procedures of apattern forming method of a second embodiment.

As a resist material, a copolymer represented by Chemical Formula 10dissolved in diglyme is used.

Chemical Formula 10:

First, as is shown in FIG. 2(a), similarly to the first embodiment, theresist material is spin-coated on a semiconductor substrate 200 ofsilicon; and the semiconductor substrate 200 is annealed at atemperature of 90° C. for 90 seconds, thereby forming a resist film 201with a thickness of 1 μm. At this point, no peeling is observed, and theresultant resist film 201 has satisfactory adhesion. Then, by using amask 203, the semiconductor substrate 200 is irradiated with a KrFexcimer laser 204, i.e., an energy beam, thereby transferring a patternof the mask 203 onto the resist film 201. In this manner, on the surfaceof an exposed area 201 a of the resist film 201,1,2,3,4-tetrahydronaphthyridinenimino-p-styrene sulfonate (NISS) isdissolved to generate sulfonic acid. A reaction caused through theexposure of the resist material is shown as Chemical Formula 11.

Chemical Formula 11:

An unexposed area 201 b of the resist film 201 has a basic propertyowing to the function of an amino group in Chemical Formula 10. On theother hand, in the exposed area 201 a of the resist film 201, NISS inChemical Formula 10 is dissolved into sulfonic acid having a strongacidic property, so that the basic property derived from the function ofthe amino group can be neutralized. In this case, since the unexposedarea 201 b has the strong basic property, water can be more easilyadsorbed in the unexposed area 201 b than in the exposed area 201 ahaving been neutralized. Specifically, since the unexposed area 201 bincludes the group having the strong basic property, a hydrogen bondwith water is strengthened, and water can be easily adsorbed. Incontrast, in the exposed area 201 a, a hydrogen bond with water isweakened by the neutralization, and water cannot be easily adsorbed.

Next, as is shown in FIG. 2(b), the semiconductor substrate 200 isallowed to stand in air with a relative humidity of 95% at a temperatureof 30° C. for 30 minutes, thereby supplying water vapor 205 onto thesurface of the resist film 201. In this manner, the water vapor 205 isadsorbed by the surface of the unexposed area 201 b, which can easilyadsorb water, and the adsorbed water is diffused into a deep portion,for example, at a depth of 100 nm from the surface of the unexposed area201 b of the resist film 201. Since the exposed area 201 a has beenneutralized, water cannot be easily adsorbed. Thus, a water adsorbinglayer 206 is selectively formed in the unexposed area 201 b.

Then, as is shown in FIG. 2(c), while retaining the semiconductorsubstrate 200 in the air with the relative humidity of 95% at atemperature of 30° C., vapor 207 of MTEOS, i.e., metal alkoxide, issprayed onto the surface of the resist film 201 for 3 minutes, therebyselectively forming an oxide film 208 on the surface of the unexposedarea 201 b of the resist film 201. In this case, the base derived fromthe amino group works as a catalyst in the hydrolysis and dehydration ofMTEOS, so that the oxide film 208 can be formed. Therefore, the oxidefilm 208 is formed merely in a portion where both the base serving asthe catalyst and water are present.

According to the second embodiment, in the exposed area 201 a of theresist film 201, since the amino group is neutralized by generatedsulfonic acid and loses its function as the catalyst and water cannot beeasily adsorbed, the oxide film cannot be formed. In contrast, in theunexposed area 201 b of the resist film 201, the base serving as thecatalyst is present and a sufficient amount of water has been adsorbed,the oxide film 208 can be formed.

Then, as is shown in FIG. 2(d), by using the oxide film 208 as a mask,the RIE using O₂ plasma is effected, thereby forming a resist pattern210. The RIE using O₂ plasma is effected by using a parallel platereactive ion etching system under conditions of a power of 900 W, apressure of 0.7 Pa and a flow rate of 40 SCCM.

In this embodiment, since the oxide film 208 is selectively formed inthe unexposed area 201 b alone to be used in the etching, the positivetype resist pattern 210 having a vertical section can be formed in theunexposed area 201 b.

Furthermore, since the water vapor 205 is supplied to the resist film201 in the procedure shown in FIG. 2(b), water is diffused into the deepportion from the surface of the unexposed area 201 b of the resist film201, so that the oxide film 208 can be grown toward the inside of theresist film 201. As a result, the oxide film 208 can attain a largethickness.

In addition, since MTEOS is supplied to the resist film 201 in the airwith the relative humidity of 95% in the procedure shown in FIG. 2(c),equilibrium of water can be retained so that the water having beenadsorbed by the resist film 201 can be prevented from evaporating andthat water can be supplied in a sufficient amount for the formation ofthe oxide film 208. As a result, the resultant oxide film 208 can attaina thickness sufficiently large for withstanding the RIE using O₂ plasma.

After the supply of MTEOS, the resist film 201 can be allowed to standin vacuum so as to evaporate alcohol included in the oxide film 208.Thus, the flow of the oxide film 208 can be avoided.

In this manner, the resist film 201 of the resist material including abasic group is subjected to the pattern exposure in this embodiment. Inthe exposed area 201 a, a strong acid is generated to neutralize thebasic property of the exposed area 201 a, and the oxide film 208 isselectively formed in the unexposed area 201 b alone, so as to be usedin etching the resist film 201. Accordingly, it is possible to form thepositive type fine-line resist pattern 210 having a satisfactory shape.

Also, since water is forcedly adsorbed in the unexposed area 201 bbefore forming the oxide film 208, the resultant oxide film 208 canattain a large thickness required for the dry development by the RIEusing O₂ plasma.

In the resist material used in the second embodiment, the copolymerrepresented by Chemical Formula 10 includes the amono group as the basicgroup. However, the basic group is not limited to the amino group butcan be any group having a basic property.

Furthermore, MTEOS is used as the metal alkoxide in this embodiment, butMTEOS can be replaced with any other metal alkoxide in a gas or liquidphase such as Si(OCH₃)₄(tetramethoxysilane),Si(OC₂H₅)₄(tetraethoxysilane), Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃, andZr(OC₂H₅)₃.

Also, the dry development is effected by the RIE using O₂ plasma in thisembodiment, but ECR (electron cyclotron resonance etching) using O₂plasma is adoptable instead.

Moreover, a light source for the exposure is the KrF excimer laser inthis embodiment, but an i-line, an ArF excimer laser, EB, X-rays or thelike can be used.

Furthermore, in the procedure for diffusing water in the surface of theunexposed area 201 b of the resist film 201 in this embodiment, thesemiconductor substrate 200 is allowed to stand in the water vapor, butwater in a liquid phase can be supplied to the resist film 201 on thesemiconductor substrate 200 instead. However, water can be more rapidlydiffused and the thickness of the oxide film 208 can be more increasedwhen the water is supplied in a gas phase than in a liquid phase, andhence, water is preferably supplied in a gas phase.

(Embodiment 3)

FIGS. 3(a) through 3(c), 4(a) and 4(b) are sectional views for showingprocedures of a pattern forming method of a third embodiment.

As a resist material, a copolymer represented by Chemical Formula 12dissolved in diglyme is used. A sulfonic acid generating groupselectively generates sulfonic acid through irradiation with an ArFexcimer laser, and an amine generating group selectively generates aminethrough irradiation with an i-line.

Chemical Formula 12:

First, as is shown in FIG. 3(a), similarly to the first embodiment, theresist material is spin-coated on a semiconductor substrate 300 ofsilicon, and the semiconductor substrate is annealed at a temperature of90° C. for 90 seconds, thereby forming a resist film 301 with athickness of 1 μm. At this point, no peeling is observed, and theresultant resist film 301 has satisfactory adhesion. Then, by using amask 303, the semiconductor substrate 300 is irradiated with an ArFexcimer laser 304, i.e., a first energy beam, thereby transferring apattern of the mask 303 onto the resist film 301. In this manner, on thesurface of an exposed area 301 a of the resist film 301, the sulfonicacid generating group is dissolved into sulfonic acid, and the exposedarea 301 a attains a strong acidic property. A reaction caused throughthe exposure of the resist material is shown as Chemical Formula 13.

Chemical Formula 13:

Next, as is shown in FIG. 3(b), the entire surface of the resist film301 is irradiated with an i-line 305, i.e., a second energy beam. Inthis manner, in the exposed area 301 a where the pattern has beentransferred through the irradiation with the ArF excimer laser 304,amine having a basic property is generated through the entire surfaceexposure with the i-line 305 as is shown in a reaction formula ofChemical Formula 14. Thus, the acidic property of the exposed area 301 ais neutralized.

Chemical Formula 14:

On the other hand, in an unexposed area 301 b where the pattern exposurehas not been effected through the irradiation with ArF excimer laser304, amine is generated on the surface of the resist film 301 throughthe entire surface exposure with the i-line 305 as is shown in areaction formula of Chemical Formula 15, so that the unexposed area 301b attains a basic property. At this point, since the unexposed area 301b has a strong basic property, water can be more easily adsorbed than inthe exposed area 301 a having been neutralized. Chemical Formula 15:

Then, as is shown in FIG. 3(c), the semiconductor substrate 300 isallowed to stand in air with a relative humidity of 95% at a temperatureof 30° C. for 30 minutes, thereby supplying water vapor 307 onto thesurface of the resist film 301. In this manner, the water vapor 307 isadsorbed by the surface of the unexposed area 301 b which can easilyadsorb water, and the adsorbed water is diffused into a deep portion,for example, at a depth of 100 nm from the surface of the unexposed area301 b of the resist film 301. Since the exposed area 301 a isneutralized, water cannot be easily adsorbed. Thus, a water adsorbinglayer 308 is selectively formed in the unexposed area 301 b.

Next, as is shown in FIG. 4(a), while retaining the semiconductorsubstrate 300 in the air with the relative humidity of 95% at atemperature of 30° C., vapor 309 of MTEOS, i.e., metal alkoxide, issprayed onto the surface of the resist film 301 for 3 minutes, therebyselectively forming an oxide film 310 on the surface of the unexposedarea 301 b. In this case, the base, the amino group, works as a catalystin the hydrolysis and dehydration of MTEOS, so that the oxide film 310can be formed. Therefore, the oxide film 310 is formed merely in aportion where both the base working as the catalyst and water arepresent.

According to the third embodiment, in the exposed area 301 a of theresist film 301, since amine is neutralized by generated sulfonic acidand loses its function as the catalyst and water cannot be easilyadsorbed, the oxide film cannot be formed. On the other hand, in theunexposed area 301 b of the resist film 301, since the base serving asthe catalyst is present and a sufficient amount of water has beenadsorbed, the oxide film 310 can be formed.

Then, as is shown in FIG. 4(b), by using the oxide film 310 as a mask,the RIE using O₂ plasma 311 is effected, thereby forming a resistpattern 312. The RIE using O₂ plasma is effected by using a parallelplate reactive ion etching system under conditions of a power of 900 W,a pressure of 0.7 Pa and a flow rate of 40 SCCM.

In this embodiment, since the oxide film 310 is selectively formed inthe unexposed area 301 b alone to be used in the etching, the positivetype resist pattern 312 having a vertical section can be formed in theunexposed area 301 b.

Furthermore, since the water vapor 307 is supplied to the resist film301 in the procedure shown in FIG. 3(c), water is diffused into the deepportion from the surface of the unexposed area 301 b of the resist film301, so that the oxide film 310 can be grown toward the inside of theresist film 301. As a result, the oxide film 310 can attain a largethickness. In particular, since the base is generated merely on thesurface of the resist film 301, the thickness of the water adsorbinglayer 308 can be limited to a depth where the base is generated. As aresult, water can be prevented from invading a portion below the exposedarea 301 a.

In addition, since MTEOS is supplied to the resist film 301 in the airwith the relative humidity of 95% in the procedure shown in FIG. 4(a),equilibrium of water can be retained so that the water having beenadsorbed by the resist film 301 can be prevented from evaporating andthat water can be supplied in a sufficient amount for the formation ofthe oxide film 310. As a result, the resultant oxide film 310 can attaina thickness sufficiently large for withstanding the RIE using O₂ plasma.

After the supply of MTEOS, the resist film 301 can be allowed to standin vacuum so as to evaporate alcohol included in the oxide film 310.Thus, the flow of the oxide film 310 can be avoided.

In this manner, according to the method of this embodiment, aftergenerating a strong acid in the exposed area 301 a through the patternexposure using the first energy beam, a base is generated through theentire surface exposure using the second energy beam having a differentenergy band from the first energy beam. Thus, the exposed area 301 a ofthe pattern exposure is neutralized, while the unexposed area 301 b ofthe pattern exposure attains the basic property. Therefore, the oxidefilm 310 can be selectively formed in the unexposed area 301 b of thepattern exposure, and the resist film 301 is etched by using the oxidefilm 310. As a result, it is possible to form the positive typefine-line resist pattern 312 having a satisfactory shape.

Also, since water is forcedly adsorbed in the unexposed area 301 bbefore forming the oxide film 310, the resultant oxide film 310 canattain a large thickness required for the dry development by the RIEusing O₂ plasma.

Furthermore, MTEOS is used as the metal alkoxide in this embodiment, butMTEOS can be replaced with any other metal alkoxide in a gas or liquidphase such as Si(OCH₃)₄(tetramethoxysilane),Si(OC₂H₅)₄(tetraethoxysilane), Ti(OC₂H₅)₄, Ge(OC₂H₅)₄, Al(OC₂H₅)₃, andZr(OC₂H₅)₃.

Also, the dry development is effected by the RIE using O₂ plasma in thisembodiment, but ECR (electron cyclotron resonance etching) using O₂plasma is adoptable instead.

Furthermore, in the procedure for diffusing water in the surface of theunexposed area 301 b of the resist film 301 in this embodiment, thesemiconductor substrate 300 is allowed to stand in the water vapor, butwater in a liquid phase can be supplied to the resist film 301 on thesemiconductor substrate 300 instead. However, water can be more rapidlydiffused and the thickness of the oxide film 310 can be more increasedwhen the water is supplied in a gas phase than in a liquid phase, andhence, water is preferably supplied in a gas phase.

Alternatively, the effects to form a positive type fine-line resistpattern having a satisfactory shape of the third embodiment can also beattained as follows: A copolymer which can generate a base throughirradiation with a first energy beam and an acid through irradiationwith a second energy beam is used as a resist material. Through theirradiation with the first energy beam, a desired pattern is exposed sothat the base is selectively generated in an exposed area. Then, throughthe irradiation of the entire surface with the second energy beam, theacid is generated on the entire surface of the resist film. Thus, theexposed area of the pattern exposure using the first energy beam isneutralized. Water vapor is then supplied to an unexposed area of thepattern exposure so that water can be adsorbed by the unexposed area.Then, both water vapor and alkoxysilane are supplied to the unexposedarea, thereby forming an oxide film in the unexposed area. By using theoxide film, the resist film is etched, thereby forming a resist pattern.

In the first through third embodiments, the copolymers represented byChemical Formulas 7, 10 and 12 are used as the resist materials.However, for example, a group for generating sulfonic acid representedby any of Chemical Formulas 16 through 21 can be used as the sulfonicacid generating group. Also, the sulfonic acid generating group can beappropriately replaced with a group having a strong acidic property.

Chemical Formula 16:

Chemical Formula 17:

Chemical Formula 18:

Chemical Formula 19:

Chemical Formula 20:

Chemical Formula 21:

Furthermore, as the amine generating group, for example, a group forgenerating amine represented by any of Chemical Formulas 22 through 27can be used, and the amine generating group can be appropriatelyreplaced with a group having a basic property.

Chemical Formula 22:

Chemical Formula 23:

Chemical Formula 24:

Chemical Formula 25:

Chemical Formula 26:

Chemical Formula 27:

Moreover, the ArF excimer laser is used as a light source for thepattern exposure using the first energy beam, but the ArF excimer lasercan be replaced with an i-line, a KrF excimer laser, EB, X-rays or thelike. The i-line is used as a light source for the entire surfaceexposure using the second energy beam, but the i-line can be replacedwith any other appropriate light source having a different energy bandfrom that of the first energy beam. In this case, in accordance with thekinds of the first and second energy beams to be used, the sulfonic acidgenerating group or the group having an acidic property, and the aminegenerating group or the group having a basic property can beappropriately selected.

Furthermore, in the first through third embodiments, the copolymersincluding the sulfonic acid generating group or the amine generatinggroup are used, but the copolymer can be replaced with another ternaryor higher polymer obtained by further polymerizing any of theaforementioned binary polymers with a group represented by ChemicalFormula 28 or 29.

Chemical Formula 28:

Chemical Formula 29:

What is claimed is:
 1. A pattern forming method comprising: a first stepof forming a resist film by coating a semiconductor substrate with apattern forming material including a copolymer having a first group forgenerating a base through irradiation with an energy beam and a secondgroup having an acidic property; a second step of selectivelyirradiating said resist film with said energy beam by using a maskhaving a desired pattern, generating said base in an exposed area onsaid resist film and neutralizing said generated base with said secondgroup; a third step of supplying metal alkoxide onto said resist filmand forming a metal oxide film on a surface of an unexposed area on saidresist film; and a fourth step of forming a resist pattern bydry-etching said resist film by using said metal oxide film as a mask.2. The pattern forming method of claim 1, wherein said third stepincludes a step of allowing said unexposed area on said resist film toadsorb water.
 3. The pattern forming method of claim 1, wherein saidsecond group is a group including a sulfonic acid group.
 4. The patternforming method of claim 1, wherein said copolymer is a binary copolymerrepresented by the following general formula or a ternary or highercopolymer obtained by further polymerizing said binary copolymer withanother group:

wherein R₁ indicates a hydrogen atom or an alkyl group; R₂ and R₃independently indicate a hydrogen atom, an alkyl group, a phenyl groupor an alkenyl group, or together indicate a cyclic alkyl group, a cyclicalkenyl group, a cyclic alkyl group having a phenyl group or a cyclicalkenyl group having a phenyl group; R₄ indicates a hydrogen atom or analkyl group; x satisfies a relationship of 0<x<1; and y satisfies arelationship of 0<y<1.